1. Field of the Invention
The present invention generally relates to the packaging of light-emitting device backlights. In particular, the present invention relates to a light-emitting device backlight package which requires minimal space while producing maximum luminosity.
2. Related Art
Liquid crystal displays (LCDs) are commonly used in televisions, computers, and cellular telephones to display information to their users. The most basic function of the LCD is to act as a light switch, allowing transmission of light in one mode and blocking transmission of light in a second mode. The LCD selectively modulates light from a backlight or a reflector (or a combination of both), with these modes being referred to as transmissive mode and reflective mode, respectively. Backlighting the LCD is a popular method of providing a light source for the LCD, since backlighting the LCD allows good functionality in low ambient light conditions and also provides enhanced contrast ratios. However, since conventional LCDs do not have high transmissivities (with most being less than 50% transmissive), it is important that the backlight be as efficient as possible.
There are currently a variety of backlight devices that are utilized and proposed. Important factors in the design of these devices are the configuration and their associated printed circuit boards (PCBs) relative to the light guiding plate (LGP). LED backlight devices currently available are typically of two types, which are shown in FIGS. 1 and 2.
FIG. 1 illustrates a conventional LED backlight package. In FIG. 1, the LED modules 10 are shown in a conventional configuration, i.e., they are placed at the bottom of an LGP 11, at each of the two ends of the LGP 11. Each LED module 10 emits light via a ray 12 toward the top of the LGP 11 enclosure, which then reflects as ray 13 to the end of the LGP 11 enclosure closest to the LED module 10, and then reflects back along ray 14 to travel along the length of the LGP 11. For this conventional example, the emitted light must encounter two reflections prior to traveling the length of the LGP 11. For each of these reflections, energy losses are incurred due to the native imperfect reflectivity of the surfaces. These energy losses, in addition to the inherent inefficiencies they introduce, also lead to poor luminosity along the length of the LGP 11. This situation is clearly undesirable and methods have been sought to solve these problems.
FIG. 2 illustrates another example of a conventional LED backlight package. This example seeks to solve the above problem of energy losses and low luminosity by placing LED modules 20 on the ends of an LGP 21. In this example, the light rays 22 emitted by the LED modules 20 travel directly along the length of the LGP 21. Since light rays 22 undergo no reflections, light transmission is improved. The result is greatly reduced energy losses, more energy efficiency and enhanced luminosity along the length of the LGP 21.
While the example of FIG. 2 is an improvement over that shown in FIG. 1, the new configuration has, however, created another drawback. For conventional LED backlights, heat-dissipating plates 23 are typically placed underneath of PCB 24 to dissipate the heat generated by the electronics away from the delicate circuitry. When this is done for the example of FIG. 2, the heat-dissipating plates 23 extend from the end of the LGP 21 in the longitudinal direction. This positioning is awkward and inefficient, causing critical space to be occupied by what is essentially a maintenance device, instead of using that space to contribute to the primary goal of achieving efficient light production.
FIG. 3 shows in greater detail a conventional LED module 30, which includes LENS 31, a chip 32 on top of fastener 33, and conductive wiring 34 connecting the chip 32 to PCB 35 underneath of the fastener 33. Additionally, heat-dissipating plates 36 are placed underneath of the PCB 35, to channel the heat generated by the electronics.
In order to overcome these problems, what is needed is a light-emitting device backlight package which achieves direct transmission of the emitted light in the longitudinal direction of an light guiding plate, while also minimizing the space required for the packaging, thus addressing and solving problems associated with conventional systems.